Axial gap type rotating electric machine

ABSTRACT

There is provided an axial gap type rotating electric machine which is small-sized and achieves a high motor efficiency as a drive source having a high torque using a strong magnet by reducing energy loss by an induced current. An axial gap type rotating electric machine having a yoke on a side of a rotor in a circular plate shape fixed to a rotating shaft, a yoke  23  on a side of a stator in a circular plate shape opposed to the yoke on the side of the rotor, a magnet fixed to a side of an opposed face of either one of the yokes on the side of the rotor or the side of the stator, a plurality of teeth  24  arranged on a side of an opposed face of other yoke on the side of the rotor or the side of the stator radially and opposedly to the magnet, and a coil  25  wound around each of the plurality of teeth, in which the yoke  23  has a fixing portion including a hole or a recess for inserting a portion Of the teeth to fix, and in which a resistance portion against an induced current (slit  36 )is provided at a surrounding of the fixing portion.

TECHNICAL FIELD

The present invention relates to a rotating electric machine having arotor and a stator constituting an electric motor, a generator or thelike and utilizing both operation of a motor and a generator as aregenerative brake when the rotating electric machine is used as a drivesource of a vehicle.

BACKGROUND ART

A radial gap type electric motor is used as a general electric motor ofa drive source or the like of an electric two-wheeled vehicle or thelike. The radial gap type electric motor is provided with a magnetaround an axis in a cylindrical shape on a side of, for example, arotor, and provided with a plurality of teeth opposed to a cylindricalface of the magnet on a side of a stator and wound with coils around theteeth. Therefore, a gap between opposed faces of the magnet and therespective teeth is formed in a cylindrical shape along the axis.

Meanwhile, an axial gap type electric motor is used as a rotation drivesource of an audio apparatus or the like having a comparatively smalloutput. The axial gap type electric motor is constituted by a yoke on aside of a rotor in a circular plate shape fixed to a rotating shaft, ayoke on a side of a stator in a circular plate shape opposed to the yokeon the side of the rotor, a magnet fixed to a side of an opposed face ofthe yoke of either one yoke on the side of the rotor or the side of thestator, a plurality of teeth arranged on the side of an opposed face ofother yoke on the side of the rotor or the side of the stator radiallyand opposedly to the magnet and coils wound around respective teeth.Therefore, a gap between the opposed faces of the magnet and the teethis formed in a planar shape orthogonal to an axis.

FIG. 17 is an explanatory view of a magnetic flux of an axial gap typeelectric motor of a background art. The drawing shows a magnetic fluxonly with respect to one tooth 3 and illustration thereof is omittedwith respect to left and right contiguous teeth 3.

The stator 1 is provided with a stator yoke 2 in a circular plate shapehaving a laminated member of steel plates and a plurality of teeth 3each similarly having a laminated member of steel plates which arearranged radially above the stator yoke 2. Each tooth 3 is wound with acoil (not illustrated). A rotor (not illustrated) in a circular plateshape is arranged opposedly to the teeth 3 of the stator. A magnet isfixed to the rotor at a predetermined gap from upper faces of the teeth3. Incidentally, the circular plate shape includes a circular shape anda planar ring shape (doughnut shape).

A magnetic circuit is formed between the rotor, not illustrated, and thestator, and a magnetic flux coming out from an N pole of the magnet ismade to flow to the tooth 3 and to the stator yoke 2 (arrow A) and flowto an S pole (not illustrated) of the magnet by passing other teeth 3.By energizing the coil, the tooth of that coil is excited to attract andrepulse the magnet of the rotor opposed to an upper face of the tooth.By successively switching energization of the coil, the excited teethare successively moved and the rotor is rotated along with the magnet.

According to such an axial gap type motor, opposed faces of the magnetand the teeth are orthogonal to an axial direction and therefore, alength in the axial direction becomes shorter than that of the radialgap type. Also in the case of increasing an output, the opposed facesopposed to each other via the gap can be increased without prolongingthe length in the axial direction and therefore, the constitution cancontribute to thin formation of the motor.

However, according to the above-described axial gap type electric motor,by energizing the coil, the magnetic flux flowing from the tooth 3 tothe stator yoke 2 is changed in a direction and a magnitude thereofsince the magnet on the side of the rotor is rotated and byelectromagnetic induction in accordance with an amount of the change, aninduced current B in an eddy shape is made to flow at inside of thestator yoke 2 centering on the tooth 3 at a surrounding thereof (FIG.17). The induced current B becomes Joule's heat to constitute loss ofenergy and the motor efficiency is reduced.

Although the loss of energy by the heat does not cause a serious problemin the case of a low output, when a strong magnet is used for achievinga large torque as in, for example, an electric two-wheeled vehicle, theloss is significantly increased and also a temperature rise rate isincreased to bring about high temperatures.

Therefore, although such an axial gap type electric motor is of a thintype and regarded to be preferable to mount to an axle or the like of anelectric two-wheeled vehicle, the motor efficiency is significantlyreduced in the case of the electric two-wheeled vehicle having a hightorque and using a strong magnet and therefore, the axial gap typeelectric motor is not applied as the drive source.

The invention takes a consideration of the above-described backgroundart and it is an object thereof to provide an axial gap type electricmotor which is small-sized and achieves a high motor efficiency as adrive source having a high torque using a strong magnet by reducingenergy loss by an induced current.

DISCLOSURE OF THE INVENTION

In order to achieve the above-described object, the invention providesan axial gap type rotating electric machine, including: a yoke on a sideof a rotor in a circular plate shape fixed to a rotating shaft; a yokeon a side of a stator in a circular plate shape opposed to the yoke onthe side of the rotor; a magnet fixed to a side of an opposed face ofeither one of the yokes on the side of the rotor or the side of thestator; a plurality of teeth arranged on a side of an opposed face ofother yoke on the side of the rotor or the side of the stator radiallyand opposedly to the magnet; and a coil wound around each of theplurality of teeth; wherein the yoke comprises a fixing portionincluding a hole or a recess for inserting a portion of the teeth tofix; and wherein a resistance portion against an induced current isprovided at a surrounding of the fixing portion.

According to the constitution, in the case of an induced currentgenerated in an eddy shape at a surrounding of the teeth at inside ofthe stator yoke based on a change in a magnetic flux passing the teeth,the induced current is blocked or reduced by forming the resistanceportion against the induced current of a slit or the like constitutedby, for example, cutting the yoke at the surrounding of the teeth.Therefore, an energy loss is reduced and a high motor efficiency isachieved.

Incidentally, the hole or the recess for fixing the teeth formed at theyoke may be for, for example, press-fitting or may be for simplyinserting or fitting the teeth and fixing the teeth by other means of ascrew or solder or the like. Further, the teeth may be fixedly bonded bysealing the teeth by a resin or the like. The hole penetrates the yokein a plate thickness direction and the recess does not penetrate. In thecase of the through hole, the yoke is formed by laminating steel platesall of which are perforated. In the case of the recess, the yoke isformed by laminating the perforated steel plates and laminating thesteel plates which are not perforated there below. That is, the recessis formed with the through hole to a middle of a plate thickness of theyoke.

A preferable constitution example is characterized in that theresistance portion is formed by a space portion provided at the yoke orcutting the yoke.

According to the constitution, the induced current is reduced byinterposing an air layer by cutting the yoke or forming the spaceportion at a portion of the yoke at which the induced current is made toflow. The cutting is formed by a shape separating the yoke in a state inwhich a gap is hardly present. A shape of the space portion may be ashape of a slit having a thin width or can be constituted by a pertinentshape of an elliptical shape or the like.

Another preferable constitution example is characterized in that theresistance portion is formed by a member made of a material that isdifferent from a material of the yoke.

According to the constitution, for example, the cutting or the slit isformed at the portion of the yoke at which the induced current is madeto flow, an insulating film is mounted thereto or a resin is filledthereto to thereby reduce the induced current. Or, the induced currentmay be reduced by providing an insulating property by denaturing theportion at which the induced current is made to flow by a treatment of achemical treatment, a laser treatment or the like.

Another preferable constitution example is characterized in that theresistance portion is formed on an inner peripheral side or an outerperipheral side of the fixing portion.

According to the constitution, the induced current is reduced by formingthe resistance portion of the cutting, the slit or the like on the innerperipheral side or the outer peripheral side of the fixing portionhaving a plurality of the holes or the recesses provided in a ring-likeshape at the yoke in the circular plate shape. In this case, theresistance portions may be formed on the inner peripheral side or theouter peripheral side unifiedly for all of the fixing portions or may beformed alternately on the inner peripheral side and the outer peripheralside or at every plurality of pieces thereof.

Another preferable constitution example is characterized in that theresistance portion is formed between the fixing portions contiguous toeach other.

According to the constitution, the induced current is reduced by formingthe resistance portion of the cutting, the slit or the like at thefixing portion having a plurality of the holes or the recesses providedin a ring-like shape at the yoke in the circular plate shape between thecontiguous fixing portions.

For example, with respect to a plurality of the teeth arranged by beingaligned in the ring-like shape, by forming slits by cutting the yokebetween the contiguous teeth along the circumferential direction, aninfluence on the magnetic flux flowing in the circumferential directionat inside of the yoke can be minimized. In this case, by forming theslit in the circumferential direction by connecting the holes of theteeth by constituting one set of the teeth in correspondence with 360°in an electric angle, the induced current can efficiently be blocked andthe motor efficiency can be increased.

Another preferable constitution example is characterized in that theresistance portion is formed without reaching the fixing portion and theyoke at a peripheral edge of the fixing portion is brought into acontinuous state.

According to the constitution, the resistance portion by the cutting,the slit or the like is not opened to a peripheral edge of the hole orthe recess of the fixing portion and therefore, in press-fitting theteeth to the fixing portion, deformation of the yoke is restrained andthe teeth can solidly and fixedly be held and a highly accurate gapinterval is maintained between the magnet and the teeth.

Another preferable constitution example is characterized in that theresistance portion is not formed totally from one face to other facewith respect to a direction of a plate thickness of the yoke and eitherof a side of the one face or a middle portion is not formed with respectto a direction of a plate thickness of the yoke.

According to the constitution, the resistance portion by the cutting,the slit or the like is not formed over the total of the plate thicknessof the yoke and therefore, when the teeth are press-fit to the fixingportion, deformation of the yoke is restrained and the teeth can solidlybe held fixedly thereto and a highly accurate gap interval is maintainedbetween the magnet and the teeth.

Another preferable constitution example is characterized in that theyoke fixed with the teeth is sealed by a resin mold.

According to the invention, the teeth can firmly be held fixedly bysolidifying the yoke mounted with the teeth by the resin. Further, whenthe yoke is deformed by press-fitting the teeth to the yoke, by settingthe yoke to a die in a state of correcting the deformation and makingthe resin flow thereto in molding, the yoke having highly accuratedimension and shape can be provided.

According to a preferable application example, an axial gap typeelectric motor of the invention is used as drive source of an electrictwo-wheeled vehicle.

According to the application example, by using the electric motor of theinvention as the drive source of the electric two-wheeled vehicle havinga high torque using a strong magnet, the motor efficiency can beincreased by restraining energy loss by restraining the induced current,the battery running distance can be prolonged and overheating can berestrained. Further, since thin formation in the axial direction isachieved, when attached to an axle, the electric motor can compactly bemounted in the vehicle width direction and large output is provided bythe compact shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electric two-wheeled vehicle to which theinvention is applied.

FIG. 2 is a diagram of a rear wheel portion of the electric two-wheeledvehicle of FIG. 1.

FIG. 3 is a perspective view of a constitution of an essential portionof a stator according to an embodiment of the invention.

FIG. 4 is an explanatory view of operation of the embodiment of theinvention.

FIG. 5 is a plane view of a stator yoke of the embodiment of theinvention.

FIG. 6 is a plane view of a stator yoke according to another embodimentof the invention.

FIG. 7 is a plane view of a stator yoke according to still anotherembodiment of the invention.

FIG. 8 is a shape explanatory view of still another embodiment of theinvention.

FIG. 9 illustrates sectional views of a stator yoke.

FIG. 10 illustrates explanatory views of examples of shapes of slits.

FIG. 11 is an exploded view of a stator according to an embodiment ofthe invention.

FIG. 12 is a whole perspective view of the stator of FIG. 11.

FIG. 13 is a whole sectional view of an electric motor integrated withthe stator of FIG. 12.

FIG. 14 illustrates explanatory views of an embodiment of the inventionsealed by a resin mold.

FIG. 15 is a perspective view of another embodiment of the invention.

FIG. 16 is a perspective view of still another embodiment of theinvention.

FIG. 17 is an explanatory view of an induced current in a stator of abackground art.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of embodiments of the invention withreference to the drawings as follows.

FIG. 1 is a side view of an electric two-wheeled vehicle to which anaxial gap type electric motor of the invention is applied.

The electric two-wheeled vehicle 10 is mounted with a steering shaft(not illustrated) of a handle 6 which is inserted to a head pipe 5fixedly attached to a front end of a main frame 4 and supports a frontwheel 8 via a front fork 7 connected thereto. A saddle 9 is provided ata central portion of a vehicle body and a battery 11 is fixed to themain frame 4 on a lower side of the saddle. A swing arm 13 is pivotablysupported by way of a pivot 12 via a damper 14 from a central portion toa rear side of the main frame 4. A motor case 16 is integrally formed ata rear end portion on the swing arm 13. An axial gap type electric motoraccording to the invention, mentioned later, is mounted to inside of themotor case 16 along with an axle (not illustrated) of a rear wheel 15and coaxially with the axle.

FIG. 2 is a diagram of an essential portion of a rear wheel portion ofthe electric two-wheeled vehicle.

A tire 15 a of the rear wheel 15 is mounted with a wheel 18 fixed to anaxle 17. An electric motor 19 of an axial gap type is mounted to insideof the motor case 16 integral with the swing arm 13. The electric motor19 is constituted by a rotor shaft 20, a rotor yoke 21 fixed to therotor shaft 20, a magnet 22 fixed to the rotor yoke 21, a stator yoke 23fixed to the motor case 16, a plurality of teeth 24 fixed to the statoryoke 23 by being aligned radially and opposedly to the magnet 22, and acoil 25 wound around each of the teeth 24.

One end portion of the rotor 20 is rotatably supported by the motor case16 via a bearing 26 and other end thereof is rotatably supported by theaxle 17 via a shaft support 27. The rotor shaft 20 is connected to theaxle 17 via a planetary mechanism 28. The planetary mechanism 28 per seis publicly known and constituted by a cylindrical housing 29, a ringgear 30 provided at an inner face of the housing 29, a sun gear 31provided at the rotor shaft 20, a planetary gear 32 rotated and revolvedby being brought in mesh with the sun gear 31 and the ring gear 30, acarrier 33 supporting the planetary gear 32 and a carrier support plate34 supporting the carrier 33 and integral with the axle 17. The axle 17is rotatably attached to the housing 29 via a bearing 35.

FIG. 3 is a diagram of an essential portion of a stator portion of anaxial gap type electric motor according to the invention.

A plurality of the teeth 24 each having a laminated member of steelplates are radially arranged above the stator yoke 23 in a circularplate shape (doughnut shape) having a laminated member of steel platesand is, for example, fixedly press-fit thereto. As shown in FIG. 11,mentioned later, the stator yoke 23 is formed by laminating platemembers 123 for the yoke constituted by punching steel plates (in adoughnut shape as shown in FIG. 3 in this example). Further, as shown inFIG. 11, the teeth 24 is formed by laminating plate members 124 for theteeth constituted by punching steel plates.

The plate members 124 for the teeth are laminated by superposing frontand rear plate faces 124 a. A side face 124 b in correspondence with aplate thickness of a steel plate is exposed to a side face of the tooth24 which is the laminated member. According to the example, a laminatingdirection is a radius direction (radial direction) and the tooth 24 isfixedly press-fit to the yoke 23 such that a direction of the plate face124 a constituting the face to be superposed becomes a circumferentialdirection.

The coil 25 (FIG. 2) is wound around each tooth 24. As shown in FIG. 2,mentioned above, the magnet 22 fixed to the rotor yoke 21 in thecircular plate shape is arranged opposedly to the teeth 24 with apredetermined gap therebetween. According to the embodiment, a slit 36is formed by cutting the stator yoke 23 on an outer peripheral side ofeach tooth 24.

FIG. 4 is an explanatory view of operation of the slit provided at thestator yoke.

By energizing the coil (not illustrated) wound around each tooth 24, thetooth 24 of the coil is excited to attract and repulse the magnet of therotor (not illustrated) opposed to an upper face of the tooth. Bysuccessively switching the excited coil, the rotor is made to rotate bysuccessively attracting and repulsing the magnet. At this occasion, amagnetic flux is made to flow from a side of the magnet to the teeth 24and a magnetic path is formed by passing the magnet, the predeterminedtooth 24 and the stator yoke 23. The magnetic flux forming the magneticpath is made to flow from the predetermined tooth 24 by passing thestator yoke 23 as shown by an arrow A. As explained with reference toFIG. 17, an induced current is generated at inside of the stator yoke 23at a surrounding of the tooth 24 (at a position of a dotted line in thedrawing). However, according to the embodiment, the slit 36 forconstituting an insulating layer is formed at the stator yoke 23 on anouter peripheral side of a press fit portion of a root portion of eachtooth 24 and therefore, an induced current is blocked and substantially,the induced current does not flow.

That is, the slit 36 constitutes a resistance portion against theinduced current and the induced current is blocked or reduced. Theresistance portion is not limited to a slit having a slender intervalbut may be formed by a space portion of a cut having almost no intervalor a hole having other shape or the like. Further, an insulating filmmay be interposed or an insulating agent of a resin or the like may befilled therein. Or, the induced current may be reduced by providing aninsulating property by denaturing a portion at which the induced currentflows by a treatment of a chemical treatment, a laser treatment or thelike.

FIG. 5 is a plane view of the stator yoke according to the embodiment ofthe invention.

The stator yoke 23 in the ring-like shape is formed to be penetrated bya plurality of teeth press fit holes 37. The slit 36 opened to an outerperipheral side of each press fit hole 37 is formed by cutting thestator yoke 23.

The press fit hole 37 is a fixing portion for inserting a portion of thetooth (press fit portion 24 a in FIG. 11) to fix to the yoke. The fixingportion may be a hole penetrating the yoke 23 in a plate thicknessdirection as shown in FIG. 9(A), mentioned later, or may be recess whichdoes not penetrate there through but formed with a hole to a middlethereof as shown in FIG. 9(C).

FIG. 6 is a plane view of a stator yoke according to another embodimentof the invention.

The embodiment is formed with a slit 36 by cutting an inner peripheralside of each teeth press fit hole 37 formed at a stator yoke 23. Evenwhen the inner peripheral side of each teeth press fit hole 37 is cut inthis way, similar to the example of FIG. 5, the induced current can beblocked.

FIG. 7 is a plane view of a stator yoke according to still anotherembodiment of the invention.

The embodiment is formed with a slit 36 in a circular arc shape or alinear shape by communicating central portions in a radial direction ofteeth press fit holes 37 contiguous to each other. In this way, the slit36 is formed along a circumferential direction (a direction orthogonalto the radial direction) of a stator yoke 23. By the slit 36, an inducedcurrent formed at a surrounding of the press fit hole fixed with thetooth can be blocked or reduced.

In this case, the induced current can effectively be restrained frombeing generated by forming the slit 36 by connecting a set of the teeth24 constituting 360° in an electrical angle. The example of FIG. 7 is anexample of forming an electrical angle of 360° by three pieces ofcontiguous teeth 24 (U phase, V phase, W phase) in a motor having 18slots and 12 poles and the slit 36 is formed by connecting the centralportions in the radial direction of the respective teeth press fit holes37 at every three pieces of the teeth press fit holes 37 contiguous toeach other. Further, a position of the slit 36 may also be other thanthe central portion.

FIG. 8 is an explanatory view of a shape of still another embodiment ofthe invention.

The embodiment is formed with a connecting portion 136 at an end portionof a slit such that a peripheral edge of teeth press fit hole 37 isbrought into a continuous state without opening the slit 36 to the teethpress fit hole 37 but cutting the slit 36 before the teeth press fithole. Thereby, not only the induced current is reduced but alsodeformation of the stator yoke and reduction in a force to hold thepress-fitting teeth by forming the slit 36 can be prevented. Further,although the example of drawing shows an example of applying to theembodiment of FIG. 5 formed with the slit 36 on an outer peripheral sideof the tooth, also with regard to the examples of FIG. 6 and FIG. 7,similarly, the slit 36 maybe formed without opening the slit 36 to theteeth press fit hole 37 but in a state of making the peripheral edge ofthe teeth press fit hole 37 continuous.

FIG. 9 illustrates sectional views of a portion of the yoke 23 takenalong a line X-X of FIG. 8.

As shown in FIG. 9(A), the stator yoke 23 is the laminated member of theplate members 123 for the yoke and the connecting portion 136 is formedbetween the press fit hole 37 and the slit 36.

FIG. 9(B) is a modified example of FIG. 9(A) and is an example in whichthe slit 36 is not penetrated in the plate thickness direction of theyoke 23 but is formed to a middle thereof. According to the example, thelowermost plate member 123 of the yoke is not formed with an opening forthe slit. In this way, by providing a portion in which the slit is notformed also in the plate thickness direction of the yoke along with theconnecting portion 136, an effect of preventing deformation of the yokeis increased.

FIG. 9(C) shows the press fit hole 37 in a shape of a recess in whichthe press fit hole 37 is not penetrated in the plate thickness directionof the yoke 23 but is formed to a middle thereof. According to theexample, the lowermost plate member 113 of the yoke is not formed withthe press fit hole 37.

FIG. 10(A) through 10(G) are views showing still another examples ofshapes of resistance portions against the induced current according tothe invention.

FIG. 10(A) is formed with the slits 36 alternately on the innerperipheral side and the outer peripheral side of the press fit holes 37.The slits 36 may not alternately be provided at every inner peripheralside and outer peripheral side of the press fit holes 37 but at everyplural pieces thereof.

FIG. 10(B) is formed with two of the slits 36 from a reverse directionon the outer peripheral side (or inner peripheral side). By aligning two(or more) of the slits in a labyrinth shape in a state in which endportions of the slits on one side are not opened but closed to becontinuous in this way, similar to the example of FIG. 8, not only thestrength of the yoke is maintained but also the resistance against theinduced current is increased and the effect of reducing the inducedcurrent is increased.

In FIG. 10(C), both end portions of the slits 36 in the radial directionare not opened but closed to connect. That is, in the example of FIG. 8,also with regard to the outer peripheral edge side of the yoke 23, theend portions of the slits 36 are made to be continuous similar to thoseon the inner peripheral side.

In FIG. 10(D), the slit 36 in the radial direction is inclined in askewed direction. The slit 36 may be bent.

In FIG. 10(E), between the press fit holes 37 contiguous to each other,the plurality (three in this example) of the slits 36 are provided inthe circumferential direction in a labyrinth shape similar to FIG.10(B).

In FIG. 10(F), between the press fit holes 37 contiguous to each other,the slit 36 which is made to be continuous by closing both ends thereofsimilar to FIG. 10(C) are provided in the circumferential direction.

In FIG. 10(G), a resistance portion against the induced current isconstituted by forming holes 36′, in a circular shape in place of theslits 36 on the inner peripheral side and the outer peripheral side ofthe press fit hole 37. The shape, a position and a number of theresistance portions (holes 36′) are not limited to those of the exampleof the drawing.

FIG. 11 is an exploded view of the stator according to the invention.

According to the example, the stator according to the embodiment of FIG.5 is shown. The stator yoke 23 formed with the slit 36 on the outerperipheral side of the teeth press fit hole 37 is the laminated memberof the plate members 123 for the yoke formed of steel plates. The tooth24 which is the laminated member of the plate members 124 for the teethformed of steel plates is inserted into the stator yoke 23 by passing abobbin (insulator) 38 made of an insulating member and a bobbin flange39 which are mounted at a position of each teeth press fit hole 37 ofthe stator yoke 23. The tooth 24 is fixedly held by press-fitting thepress fit portion 24 a at a lower end thereof into the teeth press fithole 37. The coil 25 is wound around the tooth 24 via the bobbin 38.

FIG. 12 is a whole perspective view of the stator according to theinvention.

As shown in FIG. 11, mentioned above, the teeth 24 wound with the coils25 via the bobbins 38 are aligned radially above the ring-like statoryoke 23 and press-fitted to be fixedly held. Thereby, the stator 1 isformed. According to the example, the slit 36 is formed at the statoryoke 23 on the outer peripheral side of each tooth 24.

FIG. 13 is a whole sectional view of an electric motor integrated withthe stator of FIG. 12.

A motor case 40 surrounding the entire motor is constituted by a frontcover 41 and a rear cover 42 in a circular plate shape and a side cover43 in a cylindrical shape. The front cover 41 is fixed with the statoryoke 23 formed with the above-described slit 36 of the invention. An endportion of the rotor shaft 20 is rotatably mounted to the front cover 41via the bearing 26. The vicinity of the outer end portion of the rotorshaft 20 is rotatably supported by the rear cover 42 via a bearing 44.The rotor yoke 21 is fixed to the rotor shaft 20. The rotor yoke 21 isfixed with the magnet 22. The teeth 24 press-fit to the stator yoke 23is arranged to be opposed to the magnet 22 via a predetermined gap Gtherebetween.

FIG. 14 shows the stator sealed by a resin mold. FIG. 14(A) is a planeview and FIG. 14(B) is a sectional view.

The yoke 23 is mounted with the plurality of teeth 24 in a ring-likeshape and each tooth 24 is wound with the coil 25 via the bobbin 38.Substantially the whole stator 1 having the yoke 23 and the teeth 24 inthis way is molded and sealed by a resin member 131. A lower face sideand a base plate attaching portion 132 of the resin mold member areformed with positioning bosses 130, 134. Numeral 135 designates a screwhole for attaching the base plate. A peripheral edge portion of theresin mold member is formed with an attaching hole 136 and mounted witha collar 137.

By sealing the stator 1 by the resin mold in this way, the teeth 24mounted with the coil or the like is firmly held fixedly by the yoke 23.Further, when the above-described various slits 36 or the like areformed in order to reduce the induced current, the yoke is liable to bedeformed in press-fitting the teeth, however, even when the yoke isdeformed, when the yoke is subjected to molding, the yoke can be set ina state of being corrected by a die and the stator can be molded in anundeformed shape having high dimensional accuracy.

When the deformation is corrected in this way, a mark 138 of a hold pinprovided at the die for correcting the yoke is formed at the mold memberof the resin mold 131. In this example, the mark 138 of the hold pin isformed on the yoke between the respective teeth 23, the portion is notprovided with the resin and a surface of the yoke is exposed. The marks138 of the hold pins are also formed on a rear face side of the stator1.

FIG. 15 is a perspective view of teeth according to another embodimentof the invention.

According to the embodiment, a laminating direction of the tooth 24 ischanged. That is, according to the example of FIG. 15, the plate face124 a (refer to both front and rear faces with respect to each sheet ofthe plate member 124) constituting the face to be superposed of therespective plate members 124 for the teeth constituting the teeth 24 ofthe laminated member is directed in the radial direction of the statoryoke 23. The side face 124 b (the face showing the plate thickness ofthe steel plate) of the plate member 124 for the teeth is arranged inthe circumferential direction of the stator yoke 23.

Even when the plate face 124 a constituting the face to be superposed ofthe respective plate members 124 for the teeth is directed in the radialdirection in this way, similar to the above-described example (FIG. 11)directing the plate face 124 a in the circumferential direction, theeffect of reducing the induced current by the slit 36 is sufficientlyachieved.

FIG. 16 is a perspective view of still another embodiment of theinvention.

According to the embodiment, gaps 45 are provided at press fit portionson an inner peripheral side and an outer peripheral side (only the innerperipheral side is illustrated) of the tooth 24 press-fitted to thestator yoke 23. Further, according to the example, with regard to asection in a rectangular shape of the press fit portion of the tooth 24,a long side thereof is directed in the radial direction and a short sidethereof is directed in the circumferential direction. In this case, theplate face 124 a constituting the face to be superposed of the platemember 124 for the teeth is arranged on the side of the short side andthe side face 124 b (face showing the plate thickness) of the platemember 124 for the teeth is arranged on the side of the long side.Therefore, the gap 45 is formed on the side of the plate face 124 aconstituting the face to be superposed of the teeth 24 and on the sideof the short side of the rectangular shape. The gap 45 is formed bynotching the teeth press fit hole 37 provided at the yoke 23.

By the gap 45, the magnetic flux passing the plate face 124 a on theside of the short side arranged in the circumferential direction isreduced, the induced current based on the magnetic flux is reduced andthe energy loss is further alleviated. Further, by arranging the sideface 124 b of each plate members 124 on the side of the long side, thelarge induced current generated on the side of the long side caneffectively be reduced by a resistance of the boundary faces of thelaminated layers.

INDUSTRIAL APPLICABILITY

As has been described above, according to the invention, in the case ofthe induced current generated in the eddy shape at the surrounding ofthe teeth at inside of the stator yoke based on the change in themagnetic flux passing the teeth, the induced current can be blocked orreduced by forming the resistance portion against the induced current byforming the slit by, for example, cutting the yoke at the surrounding ofthe teeth. Therefore, the energy loss is reduced and the high motorefficiency can be achieved.

Therefore, by using the axial gap rotating electric machine as a drivesource of an electric two-wheeled vehicle having a high torque using astrong magnet as an example of applying the invention, the motorefficiency can be increased by restraining the energy loss byrestraining the induced current, the battery running distance can beprolonged and overheating can be restrained. Further, since thinformation in the axial direction is achieved, when attached to the axle,the axial gap type rotating electric machine can compactly mounted inthe vehicle width direction and a large output is provided by thecompact shape.

1. An axial gap type rotating electric machine, comprising: a yoke on aside of a rotor in a circular plate shape fixed to a rotating shaft; ayoke on a side of a stator in a circular plate shape opposed to the yokeon the side of the rotor; a magnet fixed to a side of an opposed face ofeither one of the yokes on the side of the rotor or the side of thestator; a plurality of teeth arranged on a side of an opposed face ofother yoke on the side of the rotor or the side of the stator radiallyand opposedly to the magnet, wherein each of the plurality of teeth isformed by laminating a plurality of plate members; and a coil woundaround each of the plurality of teeth; wherein the yoke comprises afixing portion including a hole or a recess for inserting a portion ofthe teeth to fix, wherein plate surfaces of the plate members areperpendicular to a surface of the yoke having the fixing portion; andwherein a resistance portion to block induced current is formed as aslit in the yoke extending from the fixing portion to a peripheral sideof the yoke.
 2. The axial gap type rotating electric machine accordingto claim 1, wherein the fixing portion and the slit penetrate completelythrough the yoke.
 3. The axial gap type rotating electric machineaccording to claim 1, wherein the fixing portion penetrates completelythrough the yoke and the slit penetrates only partially through the yoketo a middle portion.
 4. The axial gap type rotating electric machineaccording to claim 1, wherein the fixing portion penetrates onlypartially through the yoke to a middle portion and the slit penetratescompletely through the yoke.
 5. The axial gap type rotating electricmachine according to claim 1, characterized in that the resistanceportion is formed on an inner peripheral side or an outer peripheralside of the fixing portion.
 6. The axial gap type rotating electricmachine according to claim 5, wherein the slit extends from the outerperipheral side of the fixing portion and opens to an outer peripheralside of the yoke.
 7. The axial gap type rotating electric machineaccording to claim 5, wherein the slit extends from the inner peripheralside of the fixing portion and opens to an inner peripheral side of theyoke.
 8. The axial gap type rotating electric machine according to claim5, wherein some slits extend from the inner peripheral side of thefixing portions for some teeth and open to an inner peripheral side ofthe yoke, and other slits extend from the outer peripheral portion ofthe fixing portions for other teeth and open to an outer peripheral sideof the yoke.
 9. The axial gap type rotating electric machine accordingto claim 5, wherein the slit extends from the fixing portion in adirection that is inclined or skewed relative to a radial direction. 10.The axial gap type rotating electric machine according to claim 1,characterized in that the resistance portion is formed by a spaceportion provided at the yoke or cutting the yoke.
 11. The axial gap typerotating electric machine according to claim 1, characterized in thatthe resistance portion is formed by a member made of a material that isdifferent from a material of the yoke.
 12. The axial gap type rotatingelectric machine according to claim 1, characterized in that the yokefixed with the teeth is sealed by a resin mold.
 13. An electrictwo-wheeled vehicle characterized in that an axial gap type electricmachine according to any one of claims 1-5 or 12 is used as a drivesource.
 14. An axial gap type rotating electric machine, comprising: ayoke on a side of a rotor in a circular plate shape fixed to a rotatingshaft; a yoke on a side of a stator in a circular plate shape opposed tothe yoke on the side of the rotor; a magnet fixed to a side of anopposed face of either one of the yokes on the side of the rotor or theside of the stator; a plurality of teeth arranged on a side of anopposed face of other yoke on the side of the rotor or the side of thestator radially and opposedly to the magnet, wherein each of theplurality of teeth is formed by laminating a plurality of plate members;and a coil wound around each of the plurality of teeth; wherein the yokecomprises a plurality of fixing portions including a hole or a recessfor inserting a portion of the teeth to fix, wherein plate surfaces ofthe plate members are perpendicular to a surface of the yoke having thefixing portion; and wherein a resistance portion to block inducedcurrent is formed as a slit extending circumferentially between andconnecting at least two of the fixing portions.
 15. The axial gap typerotating electric machine according to claim 14, wherein two slitsextend circumferentially between and connect a group of three fixingportions.
 16. The axial gap type rotating electric machine according toclaim 15, wherein there are plural groups of three fixing portions, eachhaving two slits extending circumferentially and connectingtherebetween.